Carbon quantum dots (CQDs) have a lateral size of below 100 nm, a discrete electronic belt, typical semiconductor characteristics, photoluminescence property, ultra-small size and nontoxicity, and thus exhibit a broad application prospect as a sensing electrode material.
Methods for synthesizing CQDs include hydrothermal method, electrochemical method, chemically stripping carbon fiber method, UV etching method, solution chemical method, ultrasonic wave method and microwave method, etc. However, due to complicated process, complex doping conditions, harsh reaction conditions, time consumption, low yield and the damage of the aromatic carbon frame, large-scale production and application of CQDs are limited. Therefore, designing a simple, effective, economical and environmental-friendly method for preparing carbon quantum dots materials has a very important research value and industrial significance.
Document (Photo-Fenton reaction of graphene oxide: A new strategy to prepare graphene quantum dots for DNA cleavage. Acs Nano 6.8 (2012): 6592-6599) reports a strategy for preparing graphene quantum dots by Fenton method, and the principle thereof is that: GO is oxidized directly by the hydroxyl radicals generated by Fenton reaction, producing a large amount of GQDs. This method is simple and convenient, but the addition of iron ions will make the separation of smaller size graphene quantum dots extremely difficult. Document (Molecular mechanism for metal-independent production of hydroxyl radicals by hydrogen peroxide and halogenated quinone. PNAS 104 (2007): 17575-17578) reports that tetrachlorobenzoquinone, which is a metabolite of chlorophenol, can react with H2O2 to produce hydroxyl radicals by a process independent of metal ions, and meanwhile halogen atoms are removed from chloroquinone for detoxification. This method has a low cost and can achieve degradation of pollutants simultaneously, and therefore is an ideal new preparation method for radicals.
However, so far, there has not been a method for preparing quantum dots using radicals produced by a metal-free catalysis.